U.S. patent application number 11/993570 was filed with the patent office on 2010-04-29 for deposition method of ternary films.
Invention is credited to Christian Dussarrat, Julien Gatineau, Kazutaka Yanagita.
Application Number | 20100104755 11/993570 |
Document ID | / |
Family ID | 35788045 |
Filed Date | 2010-04-29 |
United States Patent
Application |
20100104755 |
Kind Code |
A1 |
Dussarrat; Christian ; et
al. |
April 29, 2010 |
DEPOSITION METHOD OF TERNARY FILMS
Abstract
Method for producing a metal-containing film by introducing a
metal source which does not contain metal-C or metal-N--C s-bonds
(for example, TaCl<SUB>5</SUB>,
SEt<SUB>2</SUB>), a silicon precursor (for example,
SiH(NMe<SUB>2</SUB>)<SUB>3</SUB> or
(SiH<SUB>3</SUB>)<SUB>3</SUB>N), a nitrogen
precursor such as ammonia, a carbon source such as monomethylamine
or ethylene and a reducing agent (for example,
H<SUB>2</SUB>) into a CVD chamber and reacting same at
the surface of a substrate to produce metal containing films in a
single step.
Inventors: |
Dussarrat; Christian;
(Wilmington, DE) ; Yanagita; Kazutaka; (Ibaraki,
JP) ; Gatineau; Julien; (Ibaraki, JP) |
Correspondence
Address: |
AIR LIQUIDE;Intellectual Property
2700 POST OAK BOULEVARD, SUITE 1800
HOUSTON
TX
77056
US
|
Family ID: |
35788045 |
Appl. No.: |
11/993570 |
Filed: |
June 29, 2005 |
PCT Filed: |
June 29, 2005 |
PCT NO: |
PCT/EP2005/008196 |
371 Date: |
January 7, 2010 |
Current U.S.
Class: |
427/255.394 ;
427/255.23 |
Current CPC
Class: |
C23C 16/34 20130101 |
Class at
Publication: |
427/255.394 ;
427/255.23 |
International
Class: |
C23C 16/34 20060101
C23C016/34; C23C 16/30 20060101 C23C016/30 |
Claims
1-10. (canceled)
11. A method for forming a transition metal containing film onto a
sample, comprising the steps of. a) introducing a sample into a
deposition chamber; b) heating said sample up to a desired
temperature; c) providing a liquid or solid transition metal
source; d) providing at least one precursor source, said
precursor(s) source(s) being selected from the group essentially
consisting of a silicon source, a carbon source, a nitrogen source,
and/or a reducing source; e) vaporizing said transition metal to
form a vaporized transition metal source; f) delivering said
transition metal vapor to the chamber; g) delivering at least one
precursor vapor from the at least one precursor source to the
chamber; and h) forming a metallic film of the desired final
composition onto said sample.
12. The method of claim 11, wherein the metal transition source
comprises a chemical compound of the formula. MX.sub.m Or MX.sub.m,
AB.sub.n wherein M is a transition metal; X is an halogen,
preferably Cl; m is the oxidation state of the transition metal; A
is selected from the group consisting of O, S and N; B is a
hydrocarbon chain comprising between one and sixteen carbon atoms,
said chain being linear, branched or a cycle; and n is a number of
groups B bonded to A.
13. The method of claim 12, wherein M is a transition metal.
Preferably an early transition metal and most preferably selected
from the group consisting of early transition metals. Ta, Nb, Mo,
W, Hf.
14. The method of claim 11, wherein said silicon source comprises a
molecular structure terminated by at least one silyl (SiH.sub.3)
ligand, preferably trisilylamine N(SiH.sub.3).sub.3, silane
H(SiH.sub.3), disilane (SiH.sub.3).sub.2, trisilane
SiH.sub.2(SiH.sub.3).sub.2
15. The method of claim 11, wherein said nitrogen source is a
molecule or radical of the formula NH.sub.x with x being equal to
or lower than 3 or comprising a molecular structure terminated by
at least one silyl ligand, preferably trisilylamine
N(SiH.sub.3).sub.3, hexamethyldisilazane (also named
bis(trimethylsilyl)amine) HN(Si(CH.sub.3).sub.3).sub.2.
16. The method of claim 11, wherein said reducing source is a
molecule or radical of the formula H.sub.x, wherein x is equal to
or lower than 2.
17. The method of claim 11, wherein said carbon source comprises a
C1-C16 linear, branched or cyclic hydrocarbon into the reactor,
preferably an organic amine, most preferably monomethylamine,
dimethylamine, monopropylamine.
18. The method of claim 11, wherein said forming a metallic film
step is completed by using an atomic layer deposition process
wherein the precursors are preferably sequentially introduced.
19. The method of claim 11, wherein said source comprises a
molecular structure including two or three elements among silicon,
nitrogen and carbon, preferably an organic aminosilane such as
SiH.sub.2(NMe.sub.2).sub.2, SiH(NMe.sub.2).sub.3,
Si(NMe.sub.2).sub.4, SiH.sub.2(NEt.sub.2).sub.2,
SiH(NEt.sub.2).sub.3, Si(NEt.sub.2).sub.4
20. The method of claim 11, wherein said forming a metallic film
step is performed in a temperature range comprised between
250.degree. and 650.degree. C., and a pressure range comprised
between 0.01 to 1000 Torr.
Description
BACKGROUND
[0001] Manufacturing of semiconductor devices employs a thin
transition metal-containing film (typically tantalum nitride or
titanium nitride) between the underlying low-k dielectric layer and
the copper lines used as a barrier to prevent copper poisoning of
low-k dielectrics. It is expected that this type of film will be
employed as well as a metal electrode in combination with high-k
dielectric thin film in CMOS as it is already used as a top or
bottom electrode for memory applications. Depositing a transition
metal-containing film, with the generic formula
M.sub.xSi.sub.yN.sub.zC.sub.t, on high-k or low-k films therefore
forms either a gate electrode or a barrier layer. Typical processes
for growth of metallic films include chemical vapor deposition,
pulse chemical vapor deposition and atomic layer deposition
processes. As integrated circuit devices sizes shrink, the use of
metal-based dielectric films raises issues relative to the
compatibility of the use of these materials and polycrystalline
silicon (poly-Si), so far used as a gate electrode. A new class of
metal-based gate electrodes is today considered to overcome issues
such as depletion, cross-contamination . . . .
The application of metal silicon nitrides as a barrier layer
sandwiched between a Cu interconnect or electrode and a low-k
dielectric film is another example of the application of compounds
that contain metal and silicon. The metal nitrides have a good
conductivity and can also effectively prevent contamination of
low-k dielectric film by Cu. Moreover, the low resistance of the
barrier layer is an advantage from the standpoint of decreasing RC
delay. Metal silicon nitride films have heretofore been formed, for
example, by CVD using ammonia and metal halide (e.g., TiCl.sub.4,
TaCl.sub.5). This approach, however, requires a high thermal budget
and a high process temperature (>650.degree. C.) and is not
compatible with back-end-of-line (BEOL) processes. U.S. Pat. No.
6,602,783 discloses the use of ammonia and an amino metal precursor
(e.g., TDMAT, TDEAT, TBTDET, TAIMATA) for metal nitride film
formation by CVD The use of such amino metallic precursors has been
found to improve the film properties of, for example, CVD-TiSiN
films. It has also been found that the formation of metal nitride
films doped with small amounts of silicon by CVD using an amino
metallic precursor, silane SiH.sub.4, and ammonia is advantageous
in terms of improving the barrier properties. SiH.sub.4, however,
is a high pressure pyrophoric gas and SiH.sub.4 leaks pose a
substantial risk of causing damage. When, on the other hand,
dialkylaminosilane Si(NR.sub.1R.sub.2).sub.4 is used as the silicon
source in place of silane, one must deal with the strong potential
of the incorporation of large amounts of carbon into the film and
an increased barrier layer resistance. Nitrogen and/or
silicon-based compounds have been found very effective for that
purpose. Thus, it is desirable to develop new processes of
depositing metallic films with the required electrical properties
(adequate work function, high conductivity).
[0002] Of particular interest is therefore the formation of a
transition metal-containing film ("MSiN"), which can be either a
metal nitride, a metal silicide or a metal silicon nitride. Forming
a metallic film typically involves feeding the relevant chemicals
including a metal source, a silicon source, and a nitrogen source
(collectively referred to herein as the "precursors") in the proper
relative amounts to a deposition device wherein a substrate is held
at an elevated temperature. The precursors are fed to a deposition
chamber through a "delivery system." A "delivery system" is the
system of measuring and controlling the amounts of the various
precursors being fed to the deposition chamber. Various delivery
systems are known to one skilled in the art. Once in the deposition
chamber, the precursors react to deposit a film on the substrate in
a "forming" step. A "forming" step or steps, as used in this
application, is the step or steps wherein materials are deposited
on the substrate or wherein the molecular composition or structure
of the film on the substrate is modified. The "desired final
composition" of the film is the precise chemical composition and
atomic structure of the layer after completion of the last forming
step. Compounds of tantalum, titanium and tungsten, either as
metal, metal nitride, metal silicide or metal silicon nitride are
the most promising barrier or electrode materials. The metal source
for the forming process is typically a liquid precursor or a liquid
precursor solution containing the desired metal in a solvent.
Similarly, the silicon sources available today typically use a
liquid precursor which may have a low vapor pressure. Different
means of delivering the low vapor pressure silicon compound have
been developed that may include vaporizers, or dilution of the
precursor in an appropriate solvent.
[0003] When Atomic Layer Deposition (ALD) is used, the reactions
should be self-terminated to allow a well-controlled process and
therefore organic precursors might raise some issues such as
chemical stability of the precursor itself, reactivity for
nitridation and carbon content control. The use of metal halides
has been therefore extensively studied.
U.S. Pat. No. 6,139,922 discloses thermal & plasma CVD of Ta,
TaN, TaSi and TaSiN using fluorine-containing precursor. Examples
disclose PECVD using TaF.sub.5 with N.sub.2/H.sub.2 plasma and
thermal CVD using TaF.sub.5 with NH.sub.3. U.S. Pat. No. 6,200,893
discloses a multi-step ALD process (3 steps for nitridation) of TaN
using TaCl.sub.5 with N.sub.2/H.sub.2 radicals or with NH/NH.sub.2
radicals. More particularly, it discloses the use of hydrogen and
the nitrogen radicals in various steps of the process. However, no
process information is disclosed in the patent specification such
as the type of plasma and the process temperature used to carry out
such process. U.S. Pat. No. 6,265,311--discloses PECVD of tantalum
nitride using TaF.sub.5 or TaCl.sub.5 with N.sub.2/H.sub.2 plasma
in deposition range of 300 to 500 C. Direct RF plasma (0.1-5.0
W/cm.sup.2) is used for the deposition. U.S. Pat. No. 6,268,288
discloses thermal CVD of TaN using TaF.sub.5 or TaCl.sub.5 in
deposition range of 300 to 500 C, along with post-treatment of the
film with hydrogen containing radicals created by the RF plasma.
U.S. Pat. No. 6,410,433 discloses the use of thermal CVD of
tantalum nitride using TaCl.sub.5 with NH.sub.3/H.sub.2 gas in
deposition range of 300 to 500 C. U.S. Pat. No. 6,706,115 discloses
thermal ALD of TaN using TaX.sub.5 (X=Cl, Br, I) with
NR.sub.xH.sub.3-x including ammonia, wherein tantalum nitride thin
layers having low resistivity are obtained with a substrate
temperature between 350 and 500.degree. C.
[0004] The various documents cited hereabove relate to forming
dielectric films: however, all the processes disclosed in these
documents suffer from certain drawbacks;
[0005] Tantalum halides are known to be powders at ambient
conditions. Among them, TaF.sub.5 has the highest vapor pressure.
However, the fluorine contained in this precursor is too aggressive
to the layer underneath, especially in the case of high-k
dielectrics.
[0006] TaCl.sub.5 is a dimer, has a fair vapor pressure (0.3 Torr
at 100.degree. C.) but is solid and air sensitive, and therefore
difficult to stably deliver and handle.
[0007] It is known for the man skilled in the art that the physical
properties of a film are affected by the ratio of the metal (M) to
silicon (Si) and to nitrogen ratio, or M/Si/N. It is desirable to
be able to control the M/Si/N ratio over a broad range. Thus, it is
important to be able to vary the metal and silicon feed
independently to achieve the widest possible M/Si/N ratio
range.
[0008] Some processes use a silicon source precursor said silicon
source also containing some amount of the nitrogen that is to be
deposited. The problem encountered is that changes in the
nitrogen-containing silicon source precursor feed rate changes the
total amount of the nitrogen fed to the process (due to the
nitrogen contained in the silicon precursor). It makes it difficult
to control the film composition during the deposition process
because the silicon feed rate cannot be changed without also
affecting the total amount of nitrogen being fed to the deposition
chamber. Furthermore, the ratio of M/Si/N that can be fed is
limited by the composition of the nitrogen in the silicon source
precursor. Thus a change in the desired M/Si/N ratio may mean a
need for changing the precursor solution being fed to the
process.
[0009] Introducing a precursor having direct Ta--C bond or
Ta--N(--C) .sigma.-bond may also generate problems with the control
of the film composition, as carbon in very large amount can be
introduced. The carbon content with such precursors is frequently
higher than nitrogen content. As a result, another parameter should
be controlled, which makes difficult the tuning of the desired
properties (work function, threshold voltage, conductivity . . . ).
Nevertheless, carbon can have desirable effects on these
properties, and it is desirable to be able to control the amount
incorporated in the film.
[0010] For the foregoing reasons, it is desirable to form a film of
the final desired composition in a single forming step.
Furthermore, the film should minimize chlorine or any other halide
content and optimize the carbon content in the molecular structure.
It may be also desirable to use a metal source that is free of
metal-carbon bonds or nitrogen-carbon bonds so the carbon source
feed, the silicon source, the nitrogen source and the metal source
feed may be independently controlled.
SUMMARY
[0011] The present invention is directed to methods and
compositions that satisfy the need to form a thin film with
excellent electrical properties and high conformality. It avoids
using multiple forming steps to assure uniform coverage and high
conformality. The new chemistry proposed provides the benefit of
optimum film characteristics by ALD, CVD or pulsed CVD mode
deposition. Furthermore, the present invention provides a film that
minimizes chlorine or other halogen content and allows the
optimization of the carbon content, both of which can degrade the
electrical properties of the film. In addition, the invention
provides the ability to control the M/Si/N ratio in the films over
a broad range without changing precursor solutions.
[0012] According to the invention, there is provided a method for
forming a transition metal containing film onto a sample,
comprising the steps of: [0013] introducing a sample into a
deposition chamber [0014] heating said sample up to a desired
temperature; [0015] providing a liquid or solid transition metal
source; [0016] providing at least one precursor source, said
precursor(s) source(s) being selected from the group essentially
consisting of a silicon source, a carbon source, a nitrogen source,
and/or a reducing source; [0017] vaporizing said transition metal
to form a vaporized transition metal source; [0018] delivering said
transition metal vapor to the chamber, [0019] delivering at least
one precursor vapor from the at least one precursor source to the
chamber; and [0020] forming a metallic film of the desired final
composition onto said sample.
[0021] According to a preferred embodiment, the metal transition
source comprises a chemical compound of the formula
MX.sub.m
Or
the adduct MX.sub.m, AB.sub.n
Wherein:
[0022] M is a transition metal [0023] X is an halogen, preferably
Cl [0024] m is the oxidation state of the transition metal [0025] A
is selected from the group consisting of O, S and N [0026] B is a
hydrogen or hydrocarbon chain comprising between one and sixteen
carbon atoms, said chain being linear, branched or a cycle, n is
the number of groups B bonded to A.
[0027] According to various embodiments of the invention:
[0028] M is a transition metal preferably an early transition metal
and most preferably selected from the group consisting of Ta, Nb,
Mo, W, Hf . . . the silicon source comprises a molecular structure
terminated by at least one silyl (SiH.sub.3) ligand such as
trisilylamine, disilane or trisilane.
and/or [0029] the nitrogen source is a molecule or radical of the
formula NH.sub.x with x being equal to or lower than 3 or
comprising a molecular structure terminated by at least one silyl
ligand, such as trisilylamine, hexamethyldisilazane (also named
bis(trimethylsilyl)amine). and/or [0030] the reducing source is a
molecule or radical of the formula H.sub.x with x is equal to or
lower than 2. and/or [0031] the carbon source comprises comprises a
C.sub.1-C.sub.16 linear, branched or cyclic hydrocarbon.
[0032] Preferably, the step of forming a metallic film shall be
completed by using an atomic layer deposition process wherein the
precursors are preferably sequentially introduced into the
reactor.
[0033] According to an embodiment, the process of the invention is
based on the use of a vapor phase silicon precursor in conjunction
with a liquid phase metal precursor for the deposition of films of
the desired stoichiometry. The vapor phase silicon precursor is
sufficiently volatile at temperatures above 15.degree. C. to supply
the process as a vapor without the need of bubbling a carrier gas
through a liquid or heating it in a vaporizer. This eliminates the
control and quality problems associated with having to vaporize two
precursors (a metal containing precursor and a silicon containing
precursor) or to bubble a carrier gas through a liquid to feed the
silicon source. In addition, the vapor phase silicon precursor is
preferably not coordinated to a metal, allowing independent control
over feeding of the metal source and the silicon source. Thus, the
M/Si ratio can be easily varied over a wide range without having to
mix new precursor solutions and recalibrate the process to the new
precursor mixture. In a similar manner, the vapor phase nitrogen
precursor is not coordinated to a metal allowing independent
control over feeding of the metal source and the silicon source.
Thus, the M/N ratio can be easily varied over a wide range without
having to mix new precursor solutions and recalibrate the process
to the new precursor mixture. Furthermore, the vapor phase silicon
precursor is preferably carbon and halogen free, hence dramatically
reducing the undesirable effects of carbon and halogens in the
film. Finally, the current method according to the invention
produces a film of the desired final composition in a single
step.
[0034] The metal source is typically a liquid precursor or a liquid
precursor solution. The liquid phase precursor is injected into a
system that vaporizes it into a gas phase (forming a vaporized
transition metal source). The vaporized precursor gas phase enters
the deposition chamber where deposition occurs at an elevated
temperature. The metal source is preferably essentially consisting
of a metal bonded to 4 to 6 halogens. It is as well bonded with an
electrically "neutral molecule" forming an adduct to form a liquid
or a solid of low melting point. The neutral molecule is formed
with an element such as sulphur, oxygen, nitrogen and is bonded to
two or three alkyl groups. The adduct can decompose a temperature
which is high enough so that the precursor can be delivered
effectively either by a bubbler or a liquid injection system. It
can decompose at low temperature so that the elements included in
the neutral molecule may not be incorporated into the film. The
neutral molecule itself needs to be stable at high enough
temperature. Furthermore, the adduct is usually a monomer while the
metal halide is usually a dimer, which results in a significant
improvement of the vapor pressure.
The family of adducts is exemplified by the adduct
TaCl.sub.5,SEt.sub.2, which decomposes at about 200 C into
TaCl.sub.5 and SEt.sub.2, SEt.sub.2 being stable up to temperature
of at least 600 C. TaCl.sub.5,SEt.sub.2 is a monomer while
TaCl.sub.5 is a dimer, which results in a significant improvement
of the vapor pressure.
[0035] The silicon source of a film of the current invention is
injected into the deposition chamber effectively preferably
concurrent with the vaporized metal precursor. The silicon source
is preferably in the vapor phase at process feed conditions. That
is, the silicon source preferably flows from the source container
through the feed measurement and control system as a vapor without
the need to be vaporized or without using a carrier gas. However,
an inert gas may be used to dilute the silicon mixture if needed to
obtain even more accurate flow measurements. Preferably, the
silicon source does not contain in its molecular structure any atom
of chlorine and/or halogen, and/or deposition metals. More
preferably, the silicon source does not contain any atom in its
molecular structure of carbon. Most preferred silicon sources that
are carbon and chlorine free are, without limitation, the following
compounds or mixtures of the following compounds:
[0036] 1) Trisilylamine;
##STR00001##
[0037] 2) Disilylamine;
##STR00002##
[0038] 3) Silylamine;
##STR00003##
[0039] 4) Tris(disilyl)amine;
##STR00004##
[0040] 5) Aminodisilylamine;
##STR00005##
[0041] 6) Tetrasilyldiamine, also called tetrasilylhydrazine;
and
##STR00006##
[0042] 7) Disilane derivatives, wherein any H bonded to N may be
replaced with a SiH.sub.2--SiH.sub.3
##STR00007##
[0043] 8) Trisilane and its derivatives.
[0044] The nitrogen containing gas may also be injected into the
deposition chamber concurrently with the vaporized metal source and
the silicon source. Preferred oxygen containing gases and nitrogen
containing gases are free of carbon and/or chlorine in their
molecular structures.
[0045] The reaction of the different precursors in the deposition
chamber (reactor) leads to the formation of a film on the silicon
substrate. The composition of the film can be precisely controlled
by precisely controlling the flow rates of each of the precursors
independently (and this by controlling the ratio of flow rates).
The feed rates of the silicon and metal sources are independently
controllable, thus the M/Si and M/N ratios of the resulting film
can be controlled over a wide range without changing the
composition of the metal source or the silicon source.
[0046] It might be desirable to introduce an hydrogen source either
at any time during the deposition or during the post-treatment step
to reduce the chlorine content incorporated in the film or to
improve the film quality.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is a flow chart of a Prior Art method for forming a
MSiN film.
[0048] FIG. 2 is a flow chart of the steps of the method for
forming a MSiN film.
[0049] FIG. 3 is a flow chart of the steps of the method for
forming a MC film.
[0050] FIG. 4 is a flow chart of the steps of the method for
forming a MNC film.
[0051] FIG. 5 is a flow chart of the steps of the method for
forming a MSiNC film.
[0052] FIG. 6 is a flow chart of the steps of the method for
forming a MSiC film.
[0053] FIG. 7 is a structural drawing of the CVD tool used in
Example 1 of this invention.
[0054] FIG. 8 is a structural drawing of the CVD tool used in
Example 2 of this invention.
[0055] FIG. 9 is a structural drawing of the CVD tool used in
Examples 3 and the following ones of this invention.
REFERENCE SYMBOLS
[0056] 1 . . . silicon wafer [0057] 11 . . . deposition (CVD)
chamber [0058] 12 . . . pump [0059] 13 . . . adsorber [0060] 21 . .
. liquid container [0061] 22 . . . He gas [0062] 23 . . . liquid
mass flow controller [0063] 24 . . . mass flow controller [0064] 25
. . . vaporizer [0065] 31 . . . cylinder [0066] 32 . . . mass flow
controller [0067] 33 . . . N.sub.2 gas [0068] 41 . . . Additional
gas [0069] 42 . . . mass flow controller [0070] 43 . . . bubbler
[0071] 51 . . . bubbler [0072] 52 . . . nitrogen source [0073] 53 .
. . pressure regulator [0074] 54 . . . mass flow controller [0075]
55 . . . two-ways by-pass system [0076] 56 . . . flow control
system [0077] V3 . . . actuated valve [0078] V4 . . . actuated
valve [0079] V5 . . . actuated valve
EXAMPLES
[0080] Referring to the transition metal-containing film deposition
method of FIG. 1-6, the vaporizing step 1 comprises vaporizing a
metal source to form a vaporized metal source. The metal source of
one preferred embodiment is a precursor solution in liquid phase,
preferably a dialkylamino, an alkoxy, and/or an inorganic compound
of hafnium (Hf), zirconium (Zr), titanium (Ti), niobium (Nb),
tantalum (Ta), molybdenum, (Mo), tungsten (W) or any other
transition metal (M). Preparing and vaporizing the liquid phase
metal precursor solution is carried out in commercially available
equipment under appropriate conditions known to the man skilled in
the art.
[0081] During the feed step 2 a silicon source, a nitrogen source,
a carbon source, and a hydrogen source (collectively referred to as
the precursors sources) are fed to a deposition chamber where a
substrate (on which deposition is needed) is placed at an elevated
temperature. The deposition chamber is typically maintained between
about 300.degree. C. to about 900.degree. C. Preferably the surface
of the work piece in the deposition chamber will be between about
500.degree. C. to about 600.degree. C. The feeding of the
precursors is effectively concurrent (atomic layer deposition
involves high-speed sequential pulses of feed materials).
[0082] During the feed step 2 of the transition metal-containing
film deposition method of FIG. 1-6, the silicon source is
controllably injected into the deposition chamber effectively
concurrent with the vaporized metal source and the other precursors
or silicon film components. In one preferred embodiment, a silicon
source is in the vapor phase at process feed conditions. That is,
the silicon source of one preferred embodiment has a vapor pressure
of greater than approximately 50 torr at 20.degree. C., sufficient
to exist in the vapor phase in the feed control system without the
need for vaporization or bubbler equipment in the delivery system.
Trisilane and trisilylamine, two preferred silicon sources, may be
stored as a liquid, but have sufficient vapor pressure (greater
than 200 torr vapor pressure at 25.degree. C.) to be in the vapor
phase in the delivery system without the need to use a vaporizer or
bubbler system. Because the silicon source is in the vapor phase,
its flow rate can be accurately measured and controlled with
conventional devices know in the art, and is not affected by
deposits in a vaporizer or swings in feed conditions during
vaporization of the silicon or metal source.
[0083] Preferably, the silicon source is absent carbon or chlorine
in the molecular structure.
[0084] Preferably, the hydrogen and nitrogen gases are fed into the
deposition chamber concurrently with the silicon source.
Furthermore, the vaporized metal source is also fed concurrently in
the feed step 2. Various preferred embodiments of the MSiNC method
use nitrogen sources that are free of carbon and/or chlorine in
their molecular structures. It is not required that the nitrogen
source, the silicon source or the carbon source be fed as a
separate stream. The nitrogen source can be the same as the silicon
source or the carbon source. The nitrogen source of one preferred
embodiment is ammonia. The nitrogen source of another preferred
embodiment is trisilylamine. The nitrogen source is fed and
controlled with devices known to one skilled in the art.
[0085] The deposition and reaction of precursors in the deposition
chamber lead to the formation of the transition metal-containing
film on the heated silicon substrate during the forming step 3. One
preferred embodiment of a transition metal-containing film is a
tantalum silicon carbonitride film formed by feeding a tantalum
metal using a mixture of a metal source (such as TaCl.sub.5,
SEt.sub.2), trisilylamine and/or an amine.
[0086] The composition of the transition metal-containing film can
be controlled by varying the flow of each of the dielectric
precursors independently during the feeding step 2. Particularly,
the feed rate of the silicon source and the metal source are
independently controllable because the silicon source does not
contain any deposition metal. Thus, the silicon source feed rate
can be varied independently of the metal source feed rate to affect
the desired metal (M) to silicon (Si), to nitrogen and to carbon
ratio. Similarly, the metal source feed rate can be varied without
affecting the silicon source feed rate, also changing the M/Si/N
ratio. Because the feed rate of the silicon, the nitrogen, the
carbon and metal sources are independently controllable, the
M/Si/N/C ratio of the resulting film is controllable over a wide
range without changing the composition of the metal source or the
silicon source.
[0087] Although the present invention has been described in
considerable detail with reference to certain preferred versions
thereof, other versions are possible. For example, one or several
sources can be omitted in order to obtain tantalum, tantalum
silicide, tantalum silicon nitride (of FIG. 2), tantalum carbide
(FIG. 3), tantalum nitride, tantalum carbonitride (FIG. 4),
tantalum silicon carbide (of FIG. 6) . . . . The composition and
method may be practiced in a process other than chemical vapor
deposition or atomic layer deposition. In addition, the deposition
of dielectric films can be accomplished at a variety of temperature
and conditions. Furthermore, the invention may include a variety of
metal, silicon, carbon and nitrogen sources known in the art.
Therefore, the spirit and scope of the appended claims should not
be limited to the description of one of the preferred versions
contained herein. The intention of the applicants is to cover all
modifications, equivalents, and alternatives falling within the
spirit and scope of the invention as defined by the appended
claims.
EXAMPLES
[0088] Examples of the invention are described below with reference
to the drawings.
Example 1
[0089] This example concerns the fabrication of tantalum silicon
nitride films. The CVD tool used in this example is illustrated in
FIG. 7. In FIG. 7, a silicon wafer 1 is introduced into a CVD
chamber 11 and the desired film is formed onto the surface of the
silicon wafer 1. The CVD chamber 11 is evacuated by a pump 12. The
metal precursor, in this case tantalum pentachloride, diethyl
sulfur adduct TaCl.sub.5,SEt.sub.2, is stored in a liquid container
21. Nitrogen gas from the nitrogen source 22 is used as the carrier
gas for the TaCl.sub.5,SEt.sub.2. The TaCl.sub.5,SEt.sub.2 in the
liquid container 21 is pulled out in liquid form by the nitrogen
gas under pressure 22 through a liquid mass flow controller 23 and
reaches the vaporizer 25 where it is vaporized and mixed if
necessary with nitrogen from the nitrogen source 22 (or any other
inert gas from any source) through the MFC 24. Nitrogen from
nitrogen source 33 is also transported through a mass flow
controller into the CVD chamber 11 along with trisilylamine (TSA)
stored in a cylinder 31, and through mass flow controller 32 and
with an additional gas 41 (hydrogen gas, a reducing source) fed
through the pressure regulator 43 and the mass flow controller
42.
[0090] Thin films of tantalum silicon nitride films were produced
under the following conditions using the described CVD tool.
Pressure=1 torr, temperature=600.degree. C., TaCl.sub.5,SEt.sub.2
flow rate=0.5 ccm, N.sub.2 flow rate (vaporizer)=20 sccm, TSA flow
rate=5 sccm, H.sub.2 flow rate=10 sccm, N.sub.2 flow rate=100
sccm.
Example 2
[0091] This example concerns the fabrication of tantalum silicon
nitride films. The CVD tool used in this example is illustrated in
FIG. 8. On FIG. 8, the same devices as on FIG. 7 bear the same
numerical references. The CVD tool used in this example is
illustrated in FIG. 7. In FIG. 8, a silicon wafer 1 is introduced
into a CVD chamber 11 that is provided with heating means 2 over
its circumference and the desired film is formed onto the surface
of the silicon wafer 1. The CVD chamber 11 is evacuated by a pump
12. The metal precursor, in this case tantalum pentachloride,
diethyl sulfur adduct TaCl.sub.5,SEt.sub.2, is stored in a liquid
container 21. Nitrogen gas from the nitrogen source 22 is used as
the carrier gas for the TaCl.sub.5,SEt.sub.2. The
TaCl.sub.5,SEt.sub.2 in the liquid container 21 is pulled out in
liquid form by the nitrogen gas under pressure 22 through a needle
valve, a liquid mass flow controller 23 and reaches the vaporizer
25 where it is vaporized and mixed if necessary with nitrogen from
the nitrogen source 22 (or any other inert gas from any source)
through the MFC 24, Trisilylamine (TSA) stored in a cylinder 31 is
also transported through a mass flow controller (MFC) 32 into the
CVD chamber 11 along with an additional gas 41 (ammonia gas, a
nitrogen source) fed through the controllable value 43 and the mass
flow controller 42.
[0092] Thin films of tantalum silicon nitride films were produced
under the following conditions using the described CVD tool.
Pressure=1 torr, temperature=500.degree. C., TaCl.sub.5,SEt.sub.2
flow rate=0.5 ccm, TSA flow rate=5 sccm, NH.sub.3 flow rate=20
sccm, N.sub.2 flow rate=100 sccm.
Example 3
[0093] This example concerns the fabrication of tantalum silicon
nitride films. The CVD tool used in this example is illustrated in
FIG. 9. In FIG. 9, a silicon wafer 1 is introduced into a CVD
chamber 11 that is provided with heating means 2 over its
circumference and the desired film is formed onto the surface of
the silicon wafer 1. The CVD chamber 11 is evacuated by a pump 12.
The metal precursor, in this case tantalum pentachloride, diethyl
sulfur adduct TaCl.sub.5,SEt.sub.2, is stored in a liquid container
51. TaCl.sub.5,SEt.sub.2 vapor is fed to the CVD chamber 11 by
bubbling nitrogen from the nitrogen source 52, said nitrogen
flowing through the pressure regulator 53, the MFC 54, the two ways
by-pass system 55, then through the liquid source 51. The mixture
of metal precursor and/or nitrogen is then fed to the reactor
through the control system 56. Trisilylamine (TSA) stored in a
cylinder 31, is fed through mass flow controller 32. An additional
gas, such as ammonia gas, 41 is fed through the mass flow
controller 42.
[0094] Tantalum silicon nitride films were produced under the
following conditions using the described CVD tool.
Mode 3-1
[0095] Pressure=1 torr, temperature=470.degree. C.,
TaCl.sub.5,SEt.sub.2 flow rate=0.5 sccm, TSA flow rate=4 sccm,
NH.sub.3 flow rate=5 sccm, N.sub.2 flow rate=100 sccm. Using this
set of conditions, tantalum silicon nitride with component ratios
of Ta/Si=4:1 and Ta/N=1:1 was obtained at a film-formation rate of
10 .ANG./min.
Mode 3-2
[0096] Pressure=1 torr, temperature=550.degree. C.,
TaCl.sub.5,SEt.sub.2 flow rate=0.5 sccm, TSA flow rate=5 sccm,
NH.sub.3 flow rate=0 sccm, N.sub.2 flow rate=100 sccm. This mode
was the same as 1-1, with the exception that in this case no
ammonia was flown. Using this set of conditions, tantalum silicon
nitride with component ratios of Ta/Si=6:1 and Ta/N=2.6:1 was
obtained at a film-formation rate of 15 .ANG./min.
Example 4
[0097] This example concerns the fabrication of silicon-doped
titanium nitride films. The CVD tool used in this example is
illustrated in FIG. 9. The metal precursor, in this case titanium
tetrachloride TiCl.sub.4, is held in a bubbler 51 and TiCl.sub.4
vapor is fed to the CVD chamber 11 as described in example 3.
Trisilylamine (TSA) is held in the cylinder 31, and this TSA is
transported through the mass flow controller 32 into the CVD
chamber 11. The offgas from the CVD chamber is exhausted through an
abatement system (adsorber) 13. Silicon-doped titanium nitride
films were produced under the following conditions using the
described CVD tool.
Mode 4-1
[0098] Pressure=1 torr, temperature=625.degree. C., TiCl.sub.4 flow
rate=5 sccm, TSA flow rate=4 sccm, N.sub.2 flow rate=20 sccm,
time=15 minutes. According to AES analysis, the resulting film was
titanium nitride with the stoichiometric composition that contained
trace amounts of silicon. This film was about 4000 .ANG. thick. The
film-formation rate was approximately 270 .ANG./min.
Mode 4-2
[0099] Pressure=1 torr, temperature=550.degree. C. (this
film-formation temperature was substantially lower than the
prior-art film-formation temperatures using TiCl.sub.4/NH.sub.3),
TiCl.sub.4 flow rate=5 sccm, TSA flow rate=4 sccm, N.sub.2 flow
rate=20 sccm, time=15 minutes. According to AES analysis, the
resulting film was titanium nitride with the stoichiometric
composition that contained trace amounts of silicon. This film was
about 290 .ANG. thick. The film-formation rate was approximately 19
.ANG./min.
Example 5
Tantalum Silicide Films
[0100] This example concerns the fabrication of tantalum silicon
nitride films. The CVD tool used in this example is illustrated in
FIG. 9. In FIG. 9, a silicon wafer 1 is introduced into a CVD
chamber 11 that is provided and the desired film is formed onto the
surface of the silicon wafer 1. The CVD chamber 11 is evacuated by
a pump 12. The metal precursor, in this case tantalum
pentachloride, diethyl sulfur adduct TaCl.sub.5,SEt.sub.2, is
stored in a liquid container 51. TaCl.sub.5,SEt.sub.2 vapor is fed
to the CVD chamber 11 by bubbling nitrogen from the nitrogen source
52, said nitrogen flowing through the pressure regulator 53, the
MFC 54, the two ways by-pass system 55, then through the liquid
source 51. The mixture of metal precursor and/or nitrogen is then
fed to the reactor through the control system 56, Trisilane stored
in a cylinder 31, is fed through mass flow controller 32. An
additional gas, here ammonia gas (nitrogen source), 41 is fed
through the mass flow controller 42.
[0101] Tantalum silicon nitride films were produced under the
following conditions using the described CVD tool:
Pressure=1 torr, temperature=430.degree. C., TaCl.sub.5,SEt.sub.2
flow rate=0.5 sccm, Trisilane flow rate=5 sccm, NH.sub.3 flow
rate=5 sccm, N.sub.2 flow rate=120 sccm. Using this set of
conditions, tantalum silicon nitride with component ratios of
Ta/Si=4:5 and Ta/N=4:1 was obtained at a film-formation rate of 10
.ANG./min.
Example 6
Deposition of Tantalum Silicon Carbonitride
[0102] The CVD tool used in this example is illustrated in FIG. 9.
In FIG. 9, a silicon wafer 1 is introduced into a CVD chamber 11
that is provided and the desired film is formed onto the surface of
the silicon wafer 1. The CVD chamber 11 is evacuated by a pump 12.
The metal precursor, in this case tantalum pentachloride, diethyl
sulfur adduct TaCl.sub.5,SEt.sub.2, is stored in a liquid container
51. TaCl.sub.5,SEt.sub.2 vapor is fed to the CVD chamber 11 by
bubbling nitrogen from the nitrogen source 52, said nitrogen
flowing through the pressure regulator 53, the MFC 54, the two ways
by-pass system 55, then through the liquid source 51. The mixture
of metal precursor and/or nitrogen is then fed to the reactor
through the control system 56. Trisilane stored in a cylinder 31,
is fed through mass flow controller 32. An additional gas, here
monomethylamine (MMA) gas (carbon and nitrogen source), 41 is fed
through the mass flow controller 42.
[0103] Tantalum silicon carbonitride films were produced under the
following conditions using the described CVD tool:
Pressure=1 torr, temperature=430.degree. C., TaCl.sub.5,SEt.sub.2
flow rate=0.5 sccm, Trisilane flow rate=5 sccm, MMA flow rate=5
sccm, N.sub.2 flow rate=120 sccm.
[0104] Using this set of conditions, tantalum silicon nitride with
component ratios of Ta/Si=1:4,Ta/N=2:1, Ta/C=2:1 was obtained.
Example 7
Deposition of Tantalum Carbonitride
[0105] The CVD tool used in this example is illustrated in FIG. 9.
In FIG. 9, a silicon wafer 1 is introduced into a CVD chamber 11
that is provided and the desired film is formed onto the surface of
the silicon wafer 1. The CVD chamber 11 is evacuated by a pump 12.
The metal precursor, in this case tantalum pentachloride, diethyl
sulfur adduct TaCl.sub.5,SEt.sub.2, is stored in a liquid container
51. TaCl.sub.5,SEt.sub.2 vapor is fed to the CVD chamber 11 by
bubbling nitrogen from the nitrogen source 52, said nitrogen
flowing through the pressure regulator 53, the MFC 54, the two ways
by-pass system 55, then through the liquid source 51. The mixture
of metal precursor and/or nitrogen is then fed to the reactor
through the control system 56. Hydrogen stored in a cylinder 31, is
fed through mass flow controller 32. An additional gas, here
monomethylamine (MMA) gas (carbon and nitrogen source), 41 is fed
through the mass flow controller 42.
[0106] Tantalum carbonitride films were produced under the
following conditions using the described CVD tool:
Pressure=5 torr, temperature=600.degree. C., TaCl.sub.5,SEt.sub.2
flow rate=0.5 sccm, H.sub.2 flow rate=5 sccm, MMA flow rate=5 sccm,
N.sub.2 flow rate=200 sccm.
[0107] Using this set of conditions, tantalum silicon nitride with
component ratios of Ta/N=1:1, Ta/C=4:1 was obtained.
Example 8
Atomic Layer Deposition of Tantalum Silicon Nitride Films
[0108] This example concerns the fabrication of tantalum silicon
nitride films. The deposition tool used in this example is
illustrated in FIG. 9. In FIG. 9, a silicon wafer 1 is introduced
into a deposition chamber 11 that is provided with heating means 2
over its circumference and the desired film is formed onto the
surface of the silicon wafer 1. The deposition chamber 11 is
evacuated by a pump 12. The metal precursor, in this case tantalum
pentachloride, diethyl sulfur adduct TaCl.sub.5,SEt.sub.2, is
stored in a liquid container 51. TaCl.sub.5,SEt.sub.2 vapor is fed
to the deposition chamber 11 by bubbling nitrogen from the nitrogen
source 52, said nitrogen flowing through the pressure regulator 53,
the MFC 54, the two ways by-pass system 55, then through the liquid
source 51. The mixture of metal precursor and/or nitrogen is then
fed to the reactor through the control system 56, sequentially
introduced into the deposition chamber 11 by opening/closing the
actuated valve V5. Trisilylamine (TSA) stored in a cylinder 31, is
fed through mass flow controller 32, sequentially introduced into
the deposition chamber 11 by opening/closing the actuated valve V3.
An additional gas 41, none in this case, can be fed through the
mass flow controller 42, sequentially introduced into the
deposition chamber 11 by opening/closing the actuated valve V4.
Tantalum silicon nitride films were produced under the following
conditions using the described deposition tool. Pressure=1 torr,
temperature=400.degree. C., TaCl.sub.5,SEt.sub.2 flow rate=0.25
sccm, TSA flow rate=1 sccm, N.sub.2 flow rate=200 sccm.
[0109] Using this set of conditions, tantalum silicon nitride with
component ratios of Ta/N=1:1, Ta/Si=1:8 was obtained.
* * * * *